The goal of the proposed research is to discover the general mechanisms that are involved in maintaining temporal organization within a multi-oscillator circadian system using the cockroach, Leucophaea maderae, as a model system. It has been shown that the pacemaker that drives the circadian rhythm of locomotor activity in the cockroach is composed of two bilaterally distributed and mutually coupled oscillators located in the optic lobes of the protocerebrum. The oscillators appear to control activity through entrainment of a damped secondary oscillator, and are entrained via photoreceptors in the compound eyes. The research plan encompasses four specific objectives. (1) The first is to determine the extent to which the components of a single circadian timing system are responsible for the control of two (or more) physiological distinct rhythms by comparing the anatomical and physiological organization of the circadian control system that regulates the rhythm in electroretinogram amplitude with the system that controls the activity rhythm. (2) The dynamics and temperature dependence of internal coupling between oscillators will be studied by monitoring the transient motion of the optic-lobe oscillators after their desynchronization with localized low-temperature pulses. (3) Studies on the mechanism of entrainment of the pacemaking system by light will be initiated in experiments utilizing localized lesions, electrical stimulation, and pharmacological agents to investigate the physiological and anatomical organization of the pathway. (4) Spontaneous, multi-unit activity in the central nervous system will be monitored with chronically implanted electrodes to characterize rhythmicity in various locations in the CNS, to determine whether rhythmicity is expressed in the neurally isolated optic lobe, and to examine the role of the optic lobe pacemaker in regulating neural activity in the brain. The completion of these studies will provide clues to the general principles that underlie circadian organization in multicellular organisms and examine the validity of current, general models of the physiological basis of circadian organization.